Finding duplicate values in MySQL

Question

I have a table with a varchar column, and I would like to find all the records that have duplicate values in this column. What is the best query I can use to find the duplic

Answer 1

My final query incorporated a few of the answers here that helped - combining group by, count & GROUP_CONCAT.

SELECT GROUP_CONCAT(id), `magento_simple`, COUNT(*) c 
FROM product_variant 
GROUP BY `magento_simple` HAVING c > 1;

This provides the id of both examples (comma separated), the barcode I needed, and how many duplicates.

Change table and columns accordingly.